Midge tolerant wheat varieties were commercially available for the first time in 2010, but some farmers who tried them wanted to be safe rather than sorry and applied a pesticide anyway.
Although it’s easy to understand the sentiment, spraying really isn’t necessary, says Todd Hyra, western business manager with SeCan. Spraying is only worthwhile if you require pristine quality or there is extreme insect pressure, which certainly wasn’t the case in 2010, he says.
“By spraying you are really defeating the purpose of the whole technology, which is very effective in terms of reducing yield losses and damage due to wheat midge,” says Hyra, whose company handles two of the midge tolerant varieties; AC Unity VB and AC Fieldstar VB.
“By spraying you are adding cost, increasing insecticide use and taking out beneficial insects that also help reduce some of the midge population. So there are a number of reasons to try and avoid spraying.”
EXPECT SOME DAMAGE
A small amount of feeding damage is actually to be expected, says Hyra. Midge larvae must still take a bite from the wheat kernel, which quickly causes high levels of phenolic acid to be released. This deters the midge from further feeding, causing them to starve to death.
“But (farmers) will see nothing compared to what there would be if those larvae were allowed to feed freely on the kernels,” says Hyra. “Under high pressure in susceptible wheat, many larvae can be feeding on each kernel at the same time and they can be blown right out of the back of the combine, so there will be zero yield in those kernels.”
BUILT-IN RESISTANCE MANAGEMENT
There were three varieties of midge tolerant wheat on the market last year and another has been added for 2011, with more to follow. All of them are actually a blend of 90 per cent tolerant and 10 per cent susceptible (or refuge) wheat varieties, a measure designed to try and ensure both the effectiveness and longevity of the midge resistance trait.
“It’s very important to maintain
the 90/10 ratio of midge tolerant and susceptible varieties,” says John Gavloski, an entomologist with Manitoba Agriculture, Food &Rural Initiatives.
Some wheat midge are already capable of surviving the tolerant varieties, although right now they are at very low levels. Growing only midge tolerant wheat in an area would quickly increase their numbers
“If just a few of these resistant midge survive and they are the only ones that are surviving, and everything else is killed off, there is a decent chance they will get together and mate and then you have got a resistant population
developing,” explains Gavloski. “Whereas if you have susceptible wheat midge out there, and the very few resistant ones that do manage to survive end up mating with susceptible ones, then you are not getting that resistance passed on.”
Farmers who purchase AC Unity VB or AC Fieldstar VB from SeCan sign a stewardship agreement which says they will not save any seed from these varieties past the first generation.
“We have a stewardship process,” says Hyra, “and it’s all to insure that the refuge remains in place and the benefits of this technology last for many years.”
Allan and Cheryl Atcheson, who farm a few miles north of Regina, Sask., tried the AC Unity VB variety last year. Allan planted 110 acres of AC Unity VB and 640 acres of AC Lillian, the variety he usually grows because of its resistance to sawfly, a pest that has been a big problem in his area in few years.
“I was perfectly happy with Lillian wheat,” he says. “But when I heard about Unity wheat I was excited because I was hopeful it would mean one less spraying application that we would have to do.”
In fact, Atcheson didn’t spray any of his wheat for midge last year, partly because the midge pressure was forecast to be low and also due to wet conditions.
Both varieties were grown on similar land under the same conditions and were harvested in exactly the same way, which meant swathing rather than straight combining because of wet field conditions.
Growing two varieties allowed for a side-by-side comparison, which produced some interesting results. Atcheson took five samples of wheat to the local elevator, four of Lillian and one of AC Unity VB, and had them tested for protein, test weight, actual grade and grading factors.
The Lillian (for which he averaged results of the four samples) gave him 14.9 per cent protein and a test weight of 59.05 lb./bu. The midge content was 3.8 per cent and fusarium level was 3.3 per cent.
The AC Unity VB sample had a protein level of 13.9 per cent and a test weight of 60.6 lb./bu. The midge content was 0.9 per cent and fusarium level was 1.1 per cent.
“The quality definitely has something to do with the midge and the fusarium levels,” says Allan. “It only makes sense that if you have a midge damaged kernel you have more potential for the fusarium to get into that kernel, which is probably why the level of fusarium in the Unity sample was a third less than in the Lillian samples.”
The Lillian wheat’s actual grade was Canada feed, but the elevator told him that they would blend it and give him a No. 3 14.5 CWRS grade. The AC Unity VB wheat graded a poor No. 2 CWRS.
“For No. 3 CWRS they only pay up to 14.5 per cent protein,” says Atcheson. “So in my case there was a difference of $0.50 per bushel in price between the Unity and Lillian. And taking the test weight into account, on a yield of 40 bu./ ac., that’s almost a bushel an acre.”
Atcheson then did some additional math to figure out the impact on his bottom line. Using a 40 bu./ac. yield for both varieties, (which is an estimate, as he wasn’t able to complete combining of any of the fields due to wet weather), and based on the quality and the test weight, he estimates that AC Unity VB wheat gave him around $27.25 an acre advantage over Lillian.
Although he didn’t have the grain, which he is keeping for seed, tested for the refuge percentage that remained after harvest, he is fully supportive of the stewardship aspect of the new midge tolerant varieties.
Higher levels of wheat midge are expected in a condensed area of Alberta.
“I fully respect that and completely understand that it’s very important to maintain the 90/10 per cent blend to maintain the resistance,” he says.
Encouraging farmers not to save seed past one generation is a big part of the overall picture in maintaining resistance, says Gavloski.
“If you did have a heavy wheat midge population, what’s going to happen is the susceptible seed is going to get damaged, so there won’t be a 90/10 ratio anymore,” he says. “Then if you replant that again and the same thing happens you can be getting a very high percentage of resistant seed, so you are actually starting to heavily increase the odds of resistance.”
Atcheson is so pleased with his results he is planning on switching all his wheat acres to AC Unity VB in 2011. He is not alone. Hyra says SeCan surveyed 1,200 customers who tried a midge tolerant variety last year. Close to half responded, and 86 per cent of those said it had met or exceeded their expectations.
For more information on midge tolerant wheat check out www.midgetolerantwheat.ca
Based on the quality and the test weight, AC Unity VB wheat produced an extra $27.25 an acre over AC Lillian